1. Field of the Invention
The present invention relates to a communication apparatus and a method for switching channels in a beacon network; more specifically, relates to a communication apparatus and a method for transmitting data through different channels of the same beacon interval (BI). The method can be implemented by a computer program which is stored in a computer readable medium.
2. Descriptions of the Related Art
Multi-node wireless networks operating in a beacon mode adopt an operating manner similar to a time division multiple access (TDMA) to assign transmission time to different nodes. The wireless standard of IEEE 802.15.4 is one of the multi-node wireless networks. The standard of IEEE 802.15.4 is designed to satisfy wireless network requirements of supporting low data rate, low power consumption, and low cost in the market. The ZigBee Alliance established in 2002 has defined ZigBee wireless communication standard based on IEEE 802.15.4 wireless standard. ZigBee wireless communication standard has advantages of simple structure, low cost, and easy implement.
Architecture of a general beacon network is shown in FIG. 1. The beacon network comprises a gateway 101, a router 103, and a plurality of terminals 105, 107. The gateway 101 is capable of building up a beacon network, and communicates with the router 103 and the terminals 105 wirelessly. Each terminal 107 communicates with the router 103 wirelessly as well. The terminals 105, 107 comprise a transmission interface and a receiving interface, respectively. The transmission interface is configured to transmit data, i.e., to transmit data to the gateway 101 or the router 103 after the data is converted into packets. The receiving interface is configured to receive data, i.e., to receive packets from the gateway 101 or the router 103. The router 103 can relay packets to the gateway 101 or other routers. And the terminals 105, 107 do not have the capability to relay other packets.
The gateway 101 and the router 103 transmit a beacon in a fixed beacon interval. The beacon carries information of the beacon interval so that the gateway 101, the router 103, and the terminals 105, 107 can use the same beacon interval in the same channel. A time period is divided into several transmission units, such as time slots, that make the gateway 101, the router 103, and the terminals 105, 107 able to arrange the timing to transmit data packets based on the beacon interval.
In the beacon network, one channel is divided into a plurality of beacon intervals. One beacon interval is used to transmit data of all nodes in the beacon network. One beacon interval 201 of one channel is shown in FIG. 2. The beacon interval 201 can be divided into a time slot 203 for transmitting data among the gateway 101, the router 103, and the terminals 105, a time slot 205 for transmitting data between the router 207 and the terminals 107, and other unused time slots 207. The time slot 203 is further divided into a plurality of sub-time slots 2031. Each sub-time slot 2031 is assigned to one of the router 103 and the terminals 105 to transmit data. Similarly, the time slot 205 is divided into a plurality of sub-time slots 2051. Each sub-time slot 2051 is assigned to one of the terminals 107 to transmit data.
Since the IEEE 802.15.4 wireless network operating in the beacon mode uses one channel to transmit data, jamming of data packets is usually happened in the above multi-node beacon networks. And because of the limitation of physical bandwidth of the beacon network, once data is too large to be loaded on the physical network, the gateway 101 and the router 203 are forced to delay transmissions of packets or to drop packets. In addition, when the number of routers or terminals in the same beacon network increases, a transmission bandwidth of the routers and terminals will decrease so that it will take more time to transmit packets with the same size. Consequently, how to enhance the data transmission capacity and enhance data transmission speed without changing existing architecture of the beacon network is a problem required to be solved.